1. Field of Invention
The present invention relates to a photosensor. More particularly, the present invention relates to an ambient light sensor (ALS).
2. Description of Related Art
For fabricating an ambient light sensor (ALS) on a TFT-LCD panel in prior art, since the amorphous silicon (α-Si) or poly silicon (poly-Si) film has stronger sensitivity to the light with wave band between visible light (400 nm-700 nm) and near infrared (700 nm-1.1 μm), α-Si or poly-Si is usually used as the fundamental material when fabricating ALS. Nevertheless, the sensitivity of α-Si or poly-Si cannot satisfy the strict requirements nowadays, so they are gradually replaced by other novel material.
Photosensor of new generation has higher sensitivity. Take for example the photosensor having a silicon-rich oxide layer (SiOX, X<2) as a photo sense layer. When a light source illuminates the photosensor, the silicon-rich oxide layer is excited to produce electron-hole pairs and the electron-hole pairs are immediately separated by a electric field caused by a bias voltage. Then, the photo current is thus generated and output.
However, when the silicon-rich oxide layer is formed by using the low temperature deposition thin film process and the photosensor having the silicon-rich oxide layer is accordingly fabricated, if the light having a specific illumination illuminates the photosensor and the corresponding photo current is then measured, the photo current outputted from the photosensor usually fails to have a linear relationship with the light illumination. Accordingly, there could be huge errors when using the photosensor such that the photosensor cannot precisely operate.